In a Long Term Evolution (Long Term Evolution, “LTE” for short) system, an evolved base station (evolved NodeB, “eNB” for short) performs uplink and downlink data scheduling for a user equipment (User Equipment, “UE” for short) by using a physical downlink control channel (Physical Downlink Control Channel, “PDCCH” for short). A minimum time interval of the scheduling is a subframe, and a time length of the subframe is 1 millisecond. In a search space (Search Space) specific to the UE, the UE demodulates and decodes the PDCCH according to a payload size (Payload Size) of the PDCCH and a control channel element (Control Channel Element, “CCE” for short) level, and then uses a UE-specific scrambling code to descramble a cyclic redundancy check (Cyclic Redundancy Check, “CRC” for short) code to check and determine its own PDCCH, and further, performs corresponding processing for a data channel.
Depending on a transmission manner of the scheduled data channel, the PDCCH has a different downlink control information (Downlink Control Information, “DCI” for short) format. For example, a DCI format 1A denotes that a downlink data channel uses a transmit diversity transmission manner or a single-antenna-port transmission manner, and a DCI format 2C denotes a closed loop multi-input multi-output (Multiple Input Multiple Output, “MIMO” for short) transmission manner. The eNB may configure different transmission modes for the data channel of the UE. Under each transmission mode, the eNB can use only a PDCCH of a DCI format corresponding to this transmission mode to perform data scheduling for the UE. For example, two DCI formats corresponding to a transmission mode 9 are a DCI format 2C and a DCI format 1A respectively.
When closed loop MIMO transmission is used, if the UE is at a cell edge or the UE is in a high-speed moving state, a low coding rate is required for sending PDCCH signaling to the UE. Because the payload (Payload) of the DCI format 2C used to schedule the closed loop MIMO transmission is large, the low coding rate leads to increase of the PDCCH overhead and increase of the PDCCH congestion probability, and reduces the utilization rate of control channel resources of a system.
Therefore, a corresponding technical solution is required to overcome the congestion problem of the control channel, and improve the utilization rate of control channel resources of the system.